On a campaign stop in the US state of Iowa on Monday, Mr Perry said of Federal Reserve chief Mr Bernanke: "If this guy prints more money between now and the election, I don't know what y'all will do to him in Iowa, but we would treat him pretty ugly down in Texas.

"Printing more money to play politics at this particular time in American history is almost treacherous, treasonous in my opinion."

White House spokesman Jay Carney - who is also in Iowa, with President Obama on a campaign-style bus tour - said: "I certainly think threatening the Fed chairman is not a good idea.

"When you are president or running for president, you have to think about your words. The Fed's independence is important."